Investigations within this project concern the cell biology of rare human genetic disorders and normal and abnormal intracellular processes. The research goal is to gain insight into changes in molecular function that underlie various genetic metabolic disorders and work towards treatments for these illnesses. The research focuses on three groups of rare disorders: 1. Disorders of sialic acid metabolism. The key enzyme in the sialic acid biosynthesis pathway is UDP-GlcNAc 2-epimerase/ManNAc kinase (GNE). Dominant mutations in the allosteric site of GNE cause sialuria, characterized by overproduction of sialic acid. Recessive mutations in GNE cause the neuromuscular disorder GNE myopathy, also called hereditary inclusion body myopathy (HIBM). In 2007, we characterized a knock-in GNE myopathy mouse model and demonstrated that N-acetylmannosamine (ManNAc) rescues the phenotype of the homozygous mutant mice and is a promising treatment for human patients (J Clin Inv (2007) 117:1585-1594). Our ManNAc patent (No. 60/932,451) was licensed to a ManNAc manufacturer, New Zealand Pharmaceuticals. And from 2010-current preclinical and clinical studies are performed with assistance from the NIH-TRND (Therapies for Rare and Neglected Diseases) program, leading to an IND (Investigational New Drug) application and approval from FDA for the use of ManNAc in GNE myopathy patients. In 2011 a natural history study (11-HG-0218, NHGRI) of patients with GNE Myopathy was initiated, and in 2012 a Phase 1 study (T-HG-0082, NHGRI) to evaluate ManNAc as a therapy for GNE myopathy patients was started (finalized in August 2014). In October 2014 a Phase 2 study for ManNAc in Subjects with GNE Myopathy is projected to start. For these clinical studies, our group coordinates/performs sample collection, storage and research. In this last year, we established a unifying name and mutation nomenclature for GNE myopathy (Ref 1), now universally accepted in the field. We wrote an extensive book chapter on all aspects of GNE myopathy (Ref 2), and summarized all published GNE gene variants for GNE myopathy (Ref 3). Our biomarker studies identified defects in glycosphingolipid sialylation (Ref 4) and identified plasma sialylation of the Thompson-Friedenreich antigen as a robust non-invasive blood-based biomarker not only for patients with myopathy (Ref. 5) but also for other hyposialylation disorders (Ref 10, Patent pending: 61/785,094, US application). We identified a new mechanism for hyposialylation of tissues (Ref 11, Patent US application-092-2014/0-US-01) which will be further explored within the next year. In our studies of other potential human disorders of hyposialylation (other than GNE myopathy) we developed a lectin staining panel, which we applied to a variety of kidney biopsies of patients with unexplained glomerular diseases. We identified hyposialylation in 70% of these biopsies (under review). We are pursuing developing ManNAc as a therapeutic agent for these glomerular disorders. 2. Disorders of lysosome-related organelles (LRO) biogenesis. Such disorders include Hermansky-Pudlak syndrome (HPS), Chediak-Higashi syndrome (CHS), Griscelli syndrome, Gray Platelet syndrome (GPS), and other genetically unclassified disorders. Common clinical features are albinism due to defects in melanosomes and prolonged bleeding times due to platelet defects. We investigate known and unknown LRO-disorders-causing genes (by conventional and next generation sequencing techniques), with the goal of better understanding the biology of this group of diseases. To study the effects of LRO-disorders mutations, we perform cell biological studies on patient material (using immuno-fluorescence, immmuno-EM, and live cell imaging) to examine defective intracellular trafficking and sorting of proteins and organelles in cells. Such cells fail to transport certain lysosome-related organelle resident proteins to their correct destinations, and LRO-disorder gene products are generally involved in recognizing the specific vesicles that give rise to LROs. We also catalogue the clinical and genetic characteristics of the distinct subtypes of HPS and related LRO-disorders. This year we identified dysregulation of galectin-3 in HPS patients with pulmonary fibrosis (Ref. 6) and wrote a book chapter on all aspects of Griscelli syndrome (ref. 7), described neurological involvement in patients with Chediak-Higashi syndrome (submitted), and evaluated (in vitro) lentiviral HPS1 gene transfer for patients with HPS type 1 (submitted). 3. Cell biology of selected other metabolic disorder. We ide ntified novel mutations in the OPA3 gene in patients with 3-methylglutaconic aciduria (Ref. 8), used patients phenotypes to demonstrate interactions of the UPF3B and SATB2 genes (Ref 9), described the effects of autosomal recessive polycystic kidney disease/congenital hepatic fibrosis on pregnancy (Obstetrics and Gynecology 2014, in press), and reported a novel RAI1 mutation in a subject with Smith-Magenis syndrome (submitted).